Billy Newport of IBM sees a lot of similarities between his app-server-based product ObjectGrid and H-Store. In both cases, constrained tree schemas are assumed, and OLTP performance goodness ensues. A couple of points I noted on a quick skim through his blog:

He calls out RAM consumption as a challenge for this kind of architecture.

He points out that it’s a big advantage to have data called and used in the same address space.

Being based in RAM is obviously a huge part of the H-Store scheme. But so is having transaction execution be close to the database.

IBM now has both ObjectGrid and a memory-centric DBMS (solidDB) that they’ve been using as a front end for DBMS. Integration of the two could be pretty interesting.